Windows Server and Exchange upgrade recommendation?

We are a small Church with about 20 users. I have finally gotten the OK to upgrade from Server and Exchange 2003. Budget is tight. I have just enough for OS upgrade and additional memory for the servers. Currently we have two servers. I am looking for advice as to which versions of Server and Exchange would be recommended. Our users are on Windows 7 pro with Outlook 2010. I would like to give their mobile devices access to email as well. A few users are working remotely via VPN when travelling.

Typically, it is recommend to go with the latest version of Server and Exchange that is available. When you purchase licenses/CALS you are buying the latest version that is available. You can however these licenses are down gradable but when you are using the most recent version of OS and Exchange it has the longest life cycle.

Personally i would not implement a new infrastructure with older software. Go to the latest Server 2012R2 and Exchange 2013 CU8.

Also Exchange 2013 is designed to perform better on single server hardware, which will save on additional server/licensing costs.

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